I am able to hold a basic conversation in British Sign Language, don't worry, I do understand the concept.

But if you know your history, you also know that widespread sign languages are a comparatively recent thing. For most of human existence, not being able to hear/speak was equated with a mental disability. You can still see this in many languages like e.g. in the English word "dumb", which means "not being able to speak" and "not being intelligent".

Quite a few deaf children over the millennia grew up in severely understaffed orphanages, because their parents didn't want to raise a deaf child that would never return their investment. And still many of these children did grow up, in spite of never learning any meaningful language.

Sadly enough, we have a similar case in the extended family. They have a child that was born deaf, but he was only diagnosed as deaf at the age of 4 (it still baffles me how it's possible for parents to not notice that their <4 year old can't hear them). His vision is also severely impaired. His parents are conspiracy theorists, so they didn't believe the doctors and they didn't accept any medical/psychological/pedagogic help for this kid.

He's now in his mid 20s, and he can still not communicate in any meaningful way, because he never learned to. He is now in some form of daycare, and the staff there told the parents that he is too old to learn any meaningful form of communication, because he didn't when his brain was young enough to learn the concept of languages (signed or spoken).

But, I digress: My original mentioning of deaf people was to disprove that it "not hearing spoken language kills children". But the second point that I brought up (children growing up in orphanages where they are massively neglected) is something that nobody picked up, even though that's the stronger point.

Don't worry, I can hold a basic conversation in British Sign Language.

Being deaf does preclude you from hearing spoken language, which was what the mentioned experiment was about. It was specifically about a "natural human language" to emerge. That is why I brought up that point.

The better argument was the second point, which you glossed over:

Also, in many orphanages throughout the centuries, children often didn’t get much more care than described in that experiment.

If you read stories of orphanages <1900, you will see that this experiment wasn't really unique, but instead the de-facto standard for orphanages. Actually being fed and bathed might have been an improvement to many of these orphanages.

But you don't even have to go that far. Check out for example the "works" of Johanna Haarer. She wrote the main book teaching women in Nazi Germany how to raise their children. And the main points there were:

• Give the children just what they physically need
• Do not socially interact with the child at all
• If the child screams, lock it into it's room
• Emotionally deprive the child as much as possible

A whole generation was raised with these principles.

And while that created a ton of traumatized people, there was still not an incredibly high death rate among these children.

Also, check out this article: https://en.wikipedia.org/wiki/Feral_child

There are quite a few examples (especially in the "Raised in confinement" section) of children being raised without any human (or even animal) contact at all. Still they didn't just die from lacking social interaction. They were severely impaired, many of them for their whole life. But they lived unless they died of some actual medical condition.